In making carpet, particularly patterned Axminster carpet, a yarn tuft forming unit is used to provide yarn of a particular colour to each weaving point of the carpet. In conventional Axminster weaving there are two principal ways which the yarn tuft formation is carried out. The first way is on a Jacquard Axminster loom, and the second is on a spool Axminster loom.
On a gripper Jacquard Axminster loom each weaving point includes a yarn carrier which is normally fed by eight yarns usually of different colour and the Jacquard mechanism moves the carrier to bring a selected yarn to the yarn selection position. A gripper moves towards the carrier, grips the yarn at the yarn selection position then relative movement apart of the gripper and the carrier pulls a predetermined length of yarn from the carrier. The yarn is then cut to form a tuft and moved by the gripper to the weaving point. The tuft carried by the gripper is of the appropriate colour for the tuft to be supplied to the next row of carpet to be woven. For a conventional 12 foot (4 m) loom there are over a 1000 weaving points across the loom and thus the creel supplying yarn to the loom has to have the potential of carrying over 8000 yarn packages. Typically, when the creel includes measured quantities of yarn in each yarn package, an allowance of an additional eighteen metres of yarn is provided in each yarn package. Accordingly, the greater the number of yarn packages the greater the wastage. In spite of such a large creel size a designer of such carpets is relatively limited since the number of colours available for each column of tufts extending in the warp direction of the finished carpet and corresponding to a single weaving point is limited to only eight throughout each pattern repeat. Jacquards are also known in which the yarn carrier can hold sixteen different yarns. These require an even larger creel.
Spool Axminster looms provide a designer with greater flexibility. In spool Axminster looms a separate spool is provided for each row of the pattern repeat and each spool has a separate yarn winding for each weaving point along each row. Therefore, at least theoretically, the designer has an infinite number of colour choices for each column and row of each pattern repeat. However, in practice, as the number of colour choices used for each column and row of the design increases, the number of yarn packages needed for the spool winding operation also increases. Further, the spool winder must be set up differently for the winding of each spool which is time consuming. When a large number of different colours are used in both the column and row or warp and weft direction of each pattern repeat the number of different coloured yarn packages supplying the spool winder can be even larger than those on a creel of a typical Jacquard Axminster loom. The pattern repeat on spool looms is limited by the number of spools available in the spool chain. Further, there is considerably greater yarn wastage from a spool Axminster loom than a gripper Axminster loom because, on completion of a run, waste is generated from each weaving point of each row of the pattern repeat.
In both the Jacquard and spool Axminster looms a row of tufts for a complete row of the carpet is created simultaneously and transferred to the weaving point at which they are woven into a backing to produce the carpet. An entirely different approach to yarn selection for carpet production has recently been proposed in WO 95/31594. In this, it is proposed that tufts of yarn to form a row of the carpet are produced by first loading yarn tufts into a tuft carrier and then transferring the yarn tufts from the tuft carrier to the weaving points. To achieve this a large number of different tuft forming units, typically one per weaving point, are provided along the length of a path with typically each tuft forming unit being supplied with yarn of only a single colour. As the tuft carrier is moved along the path it receives tufts of appropriate colour in each of its tuft holding sites. The tuft carrier is subsequently moved so that all the tufts for each row can be gripped by grippers and transferred to the weaving point simultaneously. Thus, the tufts are not usually all formed simultaneously and hence the tuft formation is, at least to some extent, decoupled from the weaving operation. Therefore, tuft formation can take place at the same time as the weaving operation and thus tuft formation can take place substantially continuously throughout the operation of the loom. This is to be contrasted with conventional spool or gripper type looms where tuft formation takes place over only about half of each weaving cycle.
In examples given in WO 95/31594 it is suggested that partly as a result of forming the tufts throughout the entire weaving cycle it is possible to, for example, increase the speed of the tuft forming operation by four times. It is also explained that if this were possible and it was intended to operate the loom at the same speed as a conventional loom then it would be possible to reduce the size of its creel to a quarter since, in effect, each tuft forming unit would supply tufts for four weaving points. However, nowhere in this document does it exemplify an arrangement in which there are less yarn packages than the number of weaving points.
Whilst the above document specifically exemplifies only the supply of yarn of a single colour to each tuft forming unit it does disclose the theoretical possibility of providing yarn of a number of different colours to each tuft forming unit and somehow, in an unspecified way, selecting yarn of an appropriate colour for each weaving point. If this teaching is followed the creel size would not be reduced significantly. The document also discusses the theoretical possibility of holding the yarn carrier stationary whilst moving the tuft forming unit. However, neither of these theoretical possibilities are exemplified nor is it explained how they could be achieved nor what advantages would accrue.
According to this invention a carpet weaving loom includes at least one tuft forming unit for forming sequentially yarn tufts of a number of different colours, means to receive and hold at yarn tuft holding sites yarn tufts supplied sequentially by the tuft forming unit, and transfer means to transfer all of the tufts held by the yarn tuft holding sites simultaneously to their corresponding weaving points, the or each tuft forming unit supplying yarn tufts to at least twenty yarn tuft holding sites between successive operations of the transfer means.
The number of tuft forming units provided on the loom varies with the width of the loom and its required operating speed. For example, on a loom used to make carpet samples there will usually only be a single tuft forming unit and this tuft forming unit may supply tufts to, for example, three hundred, or more, tuft holding sites. On a typical twelve foot (4 m) loom there may be twelve tuft forming units each supplying tufts to less than one hundred and twenty holding sites and typically around eighty tuft holding sites. However, to be able to operate such a loom at the highest possible speed the number of tuft forming units may be increased to twenty four or even thirty with each supplying just over forty or about thirty five tuft holding sites. In the case of there being more than one tuft forming unit these are preferably subsequently equidistantly spaced across the loom.
Taking the typical case given above of a twelve toot (4 m) loom including twelve tuft forming units and assuming an equal choice of different yarns, eight, as used in a typical conventional gripper Axminster loom, the creel of such a loom only requires ninety six different yarn packages. This is nearly a hundred-fold decrease in the number of yarn packages from that required in the conventional loom. Taking the case of thirty tuft forming units this still leads to at least a thirty-fold decrease in the number of yarn packages. Reducing the size of the creel by such amounts leads to an equivalent reduction in the set-up time required to thread up the loom as well as potentially having significantly less waste as a result of a much smaller number of yarn packages on the creel.
Preferably the or each tuft forming unit is capable of forming tufts from at least eight different yarns and preferably at least ten. The number of different yarns fed to the or each tuft forming unit may be as high as twenty four or even thirty two. Increasing the number of different yarns fed to the or each tuft forming unit increases the number of yarn packages in the creel but gives a carpet designer a greater number of colour choices in each column of tufts extending in the warp direction over a conventional loom. In spite of any increase due to the greater colour choice there is always a significant reduction in the overall number of yarn packages in the creel.
Preferably the or each tuft forming unit comprises a yarn selector wheel with provision for holding a number of different yarns arranged around it, means to drive the selector wheel into a selected one of a number of angularly discrete positions to bring a selected yarn to a loading position, a puller for engaging the selected yarn at the loading position and for pulling a predetermined length of the selected yarn from the selector wheel, and a cutting mechanism to cut the selected yarn to form a tuft of predetermined length.
The yarns may be arranged around the periphery of the selector wheel generally parallel to its axis of rotation but preferably the yarns extend generally radially to the periphery of the selector wheel. Typically, such a yarn selector wheel has provision for containing more than 10 different yarns and typically 12, 16, 24 or 32 different yarns. Preferably the selector wheel is driven into and between its predetermined angular positions by a servomotor under the control of a computer.
Preferably the motion required to operate the cutter, provide opening and closing movements of the jaws of the puller, and to move the puller forwards and backwards to pull yarn from the selector wheel and in turn from the creel are all driven from a so-called xe2x80x9cgearboxxe2x80x9d forming part of the tuft forming unit. The gearbox may be driven by a servomotor under the control of a computer and in this way it can be ensured that the timing of the puller and cutter movements can be synchronised with the rotation of the selector wheel.
Alternatively a separate computer controlled servomotor may be provided to drive each motion of the cutter and puller and, in this case, the computer ensures the appropriate timing of the motions in synchronism with the rotation of the selector wheel.
Preferably the or each tuft forming unit also includes a yarn detector to ensure that yarn is present between the puller and the selector wheel after the puller has moved away from the selector wheel. Typically this yarn detector is formed by a simple light emitter and detector arrangement on opposite sides of the path of the yarn. In this way when the optical detector detects the presence of light emitted by the emitter this indicates that no yarn is present. Typically, such an indication is used to stop the operation of the loom until any problem has been rectified to ensure that each and every tuft required is formed correctly.
The carpet weaving loom may be formed in a way which is generally similar to that described in WO 95/31594 in which the or each tuft forming unit remains generally stationary and the means to receive and hold the yarn tufts at yarn tuft holding sites is formed by a tuft carrier which moves past the or each tuft forming unit. After being completely filled the tuft carrier is then transferred to a position to enable the tufts for a whole row to be taken from it simultaneously to be woven into a carpet. Alternatively, the or each tuft forming unit is arranged to traverse all or part of the width of the loom and provide tufts for the weaving points passed as the tuft forming unit or units move transversely across the loom.
As an example of the latter of these, the means to receive and hold yarn tufts may be formed by yarn tuft carriers which extend transversely across the loom. The, or each tuft forming unit moves along one of the yarn tuft carriers filling each of its tuft retention sites in turn with sequentially cut tufts, and, once all of the sites have been filled that yarn tuft carrier is moved towards the transfer means and an empty yarn tuft carrier is moved into a position adjacent the or each tuft forming unit. The yarn tuft carriers may be mounted equiangularly spaced around an axis and rotated as each yarn tuft carrier is filled. Alternatively, they may be mounted parallel to one another on an endless belt which moves the yarn tuft carriers from adjacent the or each tuft forming unit to the transfer means. In this case the transfer means correspond to the gripper arrangement of a conventional Axminster gripper loom and grip the cut tufts held in the yarn tuft carrier and move them to the weaving point at which they are woven into the carpet and released.
In another example the means to receive and hold yarn tufts may include a pocket which is associated with each weaving point and which receives the yarn tuft after it is formed by the or each tuft forming unit. Each tuft may be directed towards its associated pocket by an air flow created by applying a vacuum to the particular pocket next to receive a cut tuft. Preferably the vacuum is applied to the pockets in turn as the or each tuft forming unit moves along the row of pockets. One way of achieving this commutation between the supply of vacuum and the pockets is to provide an elongate vacuum chamber with an apertured sliding front plate; the plate being arranged to move with the tuft forming unit or units transversely across the loom so that the aperture or apertures in the plate are aligned with air exhaust ports of a particular pocket or particular pockets as the tufts for that pocket or those pockets are cut. The air flow entrains each cut tuft and guides it into its respective pocket.
Preferably the pockets are bounded at their bases by retractable pins and whilst the tufts are being formed the pins are in their forwards position defining a floor for each of the pockets. The pockets that hold each tuft are preferably formed at the upper end of a channel and when all of the pockets have been loaded with cut tufts, the pin floor is retracted and then punchers, one for each pocket, are rotated to engage each tuft and push it along its respective channel to engage it with a nose board of the loom. As the punchers withdraw, the tufts are then woven into the backing and once the punchers have withdrawn, tufts to form the next row are fed into the pockets. In this example the channels and punchers thus form the tuft transfer means.
A rapier drive for weft insertion, the shedding of the warp threads and a lay beam with beat up reeds for a beat up operation on the woven in tufts are provided in both of the above examples and, in general, they are entirely conventional in arrangement and operation.
By providing sufficient tuft forming units the loom can operate as fast as a conventional gripper Axminster loom and so weave at a rate of about forty rows of tufts per minute. With the time saved in threading up the loom and creel there is a great reduction in xe2x80x9cdowntimexe2x80x9d which leads to a considerable increase in carpet production from each loom which also typically provides an increase in the choice of colours throughout the woven carpet with less waste of yarn. It is also possible to have fewer tuft forming units and have the loom operating at a slower weaving speed than a conventional loom and still achieve a similar carpet output as a result of the shorter xe2x80x9cdowntimexe2x80x9d offsetting the slower weaving speed.
One of the most significant contributions to the speeding up of the tuft forming operation and hence to the practicality of the present invention is the arrangement of the so-called xe2x80x9cgearboxxe2x80x9d that provides the puller and cutter motions in the or each tuft forming unit. Preferably the gearbox comprises a housing carrying three parallel shafts on which are mounted three equal size pinions meshed together. One of the shafts is driven, typically by a servomotor, and all three pinions or shafts carry eccentric pins. One end of the puller is pivoted to the housing and its other end is bifurcated to provide a pair of jaws. One of the eccentric pins is connected to a rod mounted for sliding movement along the puller body and carrying an orthogonal jaw operating pin. The eccentric pin causes the puller to pivot backwards and forwards and the orthogonal jaw operating pin to move up and down. The up and down movement of the jaw operating pin between facing cam surfaces of the bifurcated jaws causes the jaws to open and close. Thus the puller moves forward, the jaws close, the puller moves backwards, the jaws open and the cycle is repeated for each rotation of the shaft. Another of the eccentric pins drives a knife blade via a link to cut the yarn to form a tuft.
Another important preferred feature of the tuft forming unit is to handle the tuft positively at all times so that it is always under control. One way of achieving this is to include a pair of cheeks spaced apart and mounted perpendicularly to the knife blade. As the knife blade is lowered to cut the yarn to form a tuft, the yarn to form the tuft is trapped between the cheeks so that, even when released from the puller and cut, it is still held positively between the cheeks. In this case the tuft forming unit preferably includes a pusher which passes between the cheeks to push the tuft out from between them. The pusher is driven via a link and a centrally pivoted first order lever from the remaining eccentric pin. The cheeks may be arranged to move up and down and also be driven from the remaining eccentric pin, or by being mounted on the knife blade. The eccentric pins are timed with respect to one another so that then yarn is held between the cheeks; the tuft is released from the jaws of the puller; the pusher initially engages the yarn whilst it is held between the cheeks; then the yarn is cut to form the tuft; and then the pusher finally pushes the cut tuft out from between the cheeks.